The invention relates to a method and apparatus for determining properties of a transmission line or channel, for instance a channel for transmitting electric or acoustic signals. It concerns also a time domain reflectometry method and an equipment for implementing this method.
In the field of telecommunications, the density of transmitted information increases regularly. This increase is not always compatible with the existing equipment, more particularly with the existing transmission lines. In order to cope with this problem, several technologies are known, for instance ADSL which means “Asymmetric Digital Subscriber Line” (or other DSL services such as HDSL and VDSL). This technology provides the possibility to transmit, with ordinary telephone lines, high data rate from the network (a central office) to the subscriber and lower data rates from the subscriber to the network.
ADSL is adapted for distances, between a central station or office and the subscriber, which are comprised between 1.5 and 6 km. HDSL is adapted for distances greater than 6 km, and VDSL is adapted for distances comprised between 0.3 and 1.5 km.
In order to be able to comply with ADSL services, the telephone line must satisfy standards of quality which are not necessarily fulfilled by all telephone lines.